KeychainCheck 2 – thorough diagnostics and tools for your keychain

Completely rewritten, this uses lower-level access to keychains, and will offer sophisticated analysis to perform more thorough diagnosis of keychain problems, and provide tools to fix them. This new release has Help, text sizing, and many improvements, and is fully compatible with Catalina and Big Sur (apart from log feature).
KeychainCheck 2.0b1 (Intel-only for Sierra, High Sierra, Mojave and Catalina)
KeychainCheck 2.0 (Universal App for Sierra, High Sierra, Mojave, Catalina, BigSur and Monterey)

KeychainCheck – a quick check of your keychain setup

If you’re suffering problems with your keychains, KeychainCheck provides a basic set of information about them which you can use in diagnosis.
Version 1.3 (Sierra, and High Sierra only)

PermissionScanner – searches folders for files which are either not writable or not readable

Performs deep search of folders containing Preferences and other files to alert you to potential problems with their permissions. An alternative to the blunt tool of repairing permissions on your whole Home folder. Now has verbose mode, and can scan any folder of your choice.
PermissionScanner 1.7 (Intel-only for Sierra, High Sierra, Mojave and Catalina)
PermissionScanner 1.8 (Universal App for Sierra, High Sierra, Mojave, Catalina, BigSur and Monterey)

RepairHomePermissions – repairs the permissions in your Home folder (no longer recommended)

Uses a procedure no longer recommended by Apple. Use at your own risk.
RepairHomePermissions 1.2 (Sierra, High Sierra and Mojave)

Known Issues:

PermissionScanner and Full Disk Access

Note: Apple no longer recommends using diskutil as part of the procedure of resetting or repairing permissions on a Home folder: the sequence detailed in RepairHomePermissions is therefore no longer recommended. See this article for the latest details.

Articles:

Tackling keychain problems with KeychainCheck 2, now a Universal App
PermissionScanner version 1.8 is now a Universal App
Apple has changed resetting permissions again
Is there a bug in macOS 10.14 and later, testing whether files are writable?
Still struggling with permissions? Try PermissionScanner 1.7
A more complex algorithm should make PermissionScanner 1.6 more reliable
Reset/repair permissions using PermissionScanner
Repairing permissions in your Home folder has changed – important change in Apple’s recommendations
Checking your keychains using KeychainCheck2